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T J van Rens

Publications and source records attributed to T J van Rens.

18 recordsLinked to original sources
PubMed1987

Accuracy and reproducibility of instrumented knee-drawer tests.

Instrumented devices for knee-drawer tests have become popular in orthopaedics relatively recently. The objective of the present study was to document the effects of several parameters on the accuracy and reproducibility of anterior-posterior (AP) drawer measurements. An instrumented knee-drawer tester for AP laxity evaluations was constructed, based on the differential displacement method, measuring shifts of the tuberosity relative to the patella. The accuracy of the AP-shift was determined with the parallel use of a highly accurate roentgen stereo photogrammetric (RSP) measurement system on two postmortem leg specimens. The effects of relative motion between patella and femur were negligible. In addition to AP shifts, significant knee flexion and tibial rotations occurred, although the foot and the thigh were fixed as well as possible. The differential displacement method was effective in circumventing this problem. The accuracy of the AP shift was greater than 10%. The reproducibility of the AP drawer parameters (shifts and compliances) was determined in normal subjects and patients. Tests were made to evaluate the effects of different observers, time sequences, and different days. In addition, effects of muscle relaxation were studied. Overall, the shift parameters at different forces were found to be reproducible to between 5 and 15%. The slopes (compliances) of the laxity curves, at different forces, were found to be reproducible between 20 and 40%. The reproducibility was principally affected by deviations in the subject positioning procedure.

Biomechanical Phenomena↗
PubMed1986

Substitution of the anterior cruciate ligament: a long-term histologic and biomechanical study with autogenous pedicled grafts of the iliotibial band in dogs.

This paper reports the experience with anterior cruciate ligament (ACL) substitution by standardized pedicled strips of the iliotibial band, fixed to the tibia and femur with a bone-peg fixation technique. Thirty-two young adult (+/- one year old) Labrador dogs were used for the experiments (58 transplant knees and six controls). The posttransplantation period ranged from day zero to three years postoperatively. Of the transplants, there were five failures. Forty-seven knees served for gross, photographic, and histologic examination. In 17 knees, the transplants were submitted to tensile testing in an Instron testing machine. The behavior of the ACL transplants was as follows: the transplants became necrotic in a short period of time, but after day four, a process of creeping substitution took place. At 12-16 weeks, a newly formed ligament was seen with a striking macroscopic resemblance to the normal ACL. However, its collagen fibers were coarser and more undulant, and they were fixed to the bony interfaces with Sharpey-like fibers. When these rather good-looking ACLs were subjected to mechanical testing and compared with normal ACLs, the results were less satisfactory. Mechanically, the substituted ACLs were 45% less stiff than normal ligaments, the yield point was at one-third, and the ultimate load was 40% of that of a normal ACL (deformation rate, 5 mm/min). Normal ACLs rupture at their tibial insertion. The transplants ruptured intraligamentarily. A striking finding was that the substituted ligament did not derotate when all the other ligamentous and capsular structures were cut. There was no torsional arrangement of their component bundles. Although the substituted ACL has an excellent histological and macroscopic appearance, its mechanical properties are inferior.

Animals↗
PubMed1986

Gentamicin-PMMA beads. Pharmacokinetic and nephrotoxicological study.

Five patients treated with gentamicin-polymethylmethacrylate (PMMA) beads were monitored during the treatment of nine to 14 days. Kinetic data of the gentamicin delivery were gathered constantly by multiple samples of blood and urine. The treatment with 48-360 beads caused a gentamicin serum concentration of 0.03-0.4 micrograms/ml and a renal excretion rate of 3-40 micrograms/min. The total amount of gentamicin excreted after the whole treatment was 20%-70%, with an in vivo half-life of 5.7-10 days. The gentamicin appeared to be released constantly during the entire treatment (nine to 14 days); the beads are kinetically slow release carriers. Despite precise measurement of tubular and glomerular renal function, no nephrotoxicity could be demonstrated. This local antibiotic gentamicin therapy may use the blood bone barrier effectively as a protection of the body against a very high local gentamicin concentration.

Adult↗
PubMed1985

Analytical stereophotogrammetric determination of three-dimensional knee-joint geometry.

An analytical stereophotogrammetric method is introduced to measure the three-dimensional geometry of articular surfaces in vitro. Information of this kind is particularly useful for mathematical joint models and anthropological studies. The method requires no specific equipment, such as a stereocomparator, contrarily to other techniques reported (e.g. Ghosh, 1983) and is relatively simple and inexpensive. The background of the method is outlined in the present paper, and results of accuracy and precision tests are presented. It is shown that an accuracy on the order of 0.2 mm (95% confidence interval) is well feasible in actual knee-joint evaluations, if the measuring procedure is conducted carefully. The method is illustrated by measuring and comparing the articular surface geometries of a bilateral pair of knee joints.

Biomechanical Phenomena↗
PubMed1985

Cranio-vertebral pathology in Down syndrome.

Cranio-vertebral malformations, especially atlanto-axial dislocation, are frequently seen in Down patients. However, symptomatic forms in mongolism are rare. Pyramidal signs have a signal value. In symptomatic malformations surgical treatment should be advised, i.e. posterior fixation after pre-operative reduction by traction or transoral odontoidectomy if no reduction is achieved.

Adolescent↗
PubMed1982

99mTc-pertechnetate uptake after total knee replacement in rheumatoid arthritis.

In 6 out of 48 non-hinged knee joint replacements in 35 patients, 99mTc04- uptake values were clearly increased compared with a control group. Measurements were performed an average of 3 years (range 9 months - 4 1/2 years) after operation. Four of the six cases showed loosening of the prosthesis at arthrotomy and one showed an infection. Tests for hypersensitivity to the different components of the prosthesis and cement were normal. Histology and immunofluorescence of the synovial membrane obtained at arthrotomy in the four operated patients showed no recurrence of the synovitis. This study indicates that there is no recurrence or only a slight recurrence of rheumatoid synovitis after total knee joint replacement of the geometric type.

Aged↗
PubMed1982

Long-term results in lumbosacral interbody fusion for spondylolisthesis.

Out of a group of 235 patients who underwent a lumbosacral interbody fusion, 24 who were operated on for spondylolisthesis and had a long follow-up period were isolated for careful clinical and radiological evaluation. All patients were examined 1 year after surgery and 10 years or more postoperatively. Bony fusion was achieved within 4 to 6 months in all cases except one. The clinical results, showed that all patients had a good or intermediate result after 1 year. After 10 years or more 20 patients still had a good result, three an intermediate result and one a poor result. Our special interest concerned the radiological behaviour of the discs above the fused segment. This was evaluated on flexion and extension films, preoperatively and 10 years postoperatively. After this period an instability, radiologically visible as a posterior shift of 3 mm or more, was found in three L4-5 segments. No instability was found in the L3-4 segments. The disc space height diminished in three cases in the L4-5 segment and in one case in the L3-4 segment. No definite conclusions could be drawn from the flexion and extension angles measured preoperatively and 10 years or more postoperatively. Analysis of the poor and intermediate results showed that low back pain may persist to some extent after previous posterior surgery. In two cases a correlation was found between narrowing and tilt of an L4-5 segment and pain. In these two cases there was also an inadequate correction of the preoperative olisthetic kyphosis. There was one case of persistent back pain without any clinical or radiological findings. Finally, of the 106 males out of the group of 235 patients, none had problems of postoperative sterility or persistent retrograde ejaculation.

Adolescent↗
PubMed1976

Strontium 87mSr bone scanning for the evaluation of total hip replacement.

In a series of seventeen patients with unilateral osteoarthritis of the hip a scintiscanning follow-up study was made before and after total hip replacement for the assessment of the normal course of the 87mSr-scintiscan. In another series of twenty-eight patients with total hip replacement a photoscan was made as a supplement for the diagnosis of loosening of one or both components of a total hip implant. In most of these cases it proved to be a useful method, especially when clinical and raidological examination was inconclusive. It is concluded that up to six months after operation increased osteoblastic activity exists; the scintiscan became normal after that time. 87mSr scintiscanning offers a safe and simple technique for the assessment of the success and stability of total hip arthroplasty. It is also a useful aid for the early detection of loosening and infection. The procedure can help in the differential diagnosis of complaints after total hip replacement.

Arthroplasty↗